Method for the rapid reaching and maintenance of a certain temperature level

ABSTRACT

Heating and temperature maintenance device including a hollow body portion containing a core housing, a material to be heated, a first chamber disposed about the core containing a first pyrotechnic composition capable, upon ignition, of rapidly heating the material to a desired temperature, a meltable metal or alloy disposed about the first chamber capable of being melted by the ignition of the first pyrotechnic composition, and a second chamber, disposed between the body periphery and the metal or alloy, containing a second pyrotechnic composition having, upon ignition, a slower burning rate than the first pyrotechnic composition and capable of maintaining the metal or alloy in a molten condition for a predetermined time.

United States Patent Heinz Gawlick.

Fuerth Bayern.

Hellmut Bendler. Nuernberg, Guenther Marondel, Erlangen. and Werner Siegelin, Stein near Nuernberg, Germany [72] lnventors [21 1 Appl, No 796,642

[22] Filed Jan. 24,1969

[45] Patented Jan. 12,1971

[7 3] Assignee Dynamit Nobel AG.,

Troisdorf (Bezirk Cologne), Germany,

- a corporation of Germany [32] Priority Jan. 25, 1968 [3 3 Germany [54] METHOD FOR THE RAPID REACHING AND MAINTENANCE OF A CERTAIN TEMPERATURE LEVEL 10 Claims, 2 Drawing Figs.

[52] U5. Cl 126/263, 44/3 [51] Int. Cl F24j H00 [50] Field of Search 126/263, 400; 44/3 [56] References Cited UNlTED STATES PATENTS 847,668 3/1907 Lang 126/263X 2,531,548 1 H1956 Bennett 126/263 Primary Examiner-Charles J. Myhre AnarneyBurgess, Dinklage and Sprung ABSTRACT: Heating and temperature maintenance device including a hollow body portion containing a core housing, a material to be heated, a first chamber disposed about the core containing a first pyrotechnic composition capable, upon ignition, of rapidly heating the material to a desired temperature, a meltable metal or alloy disposed about the firstchamber capable of being melted by the ignition of the first pyrotechnic composition, and a second chamber, disposed between the body periphery and the metal or alloy, containing a second pyrotechnic composition having, upon ignition, a slower burning rate than the first pyrotechnic composition and capable of maintaining the metal or alloy in a molten condition for a predetermined time.

PATENTED JAN 1 2 1971 VII INVENTORS HEINZ GAWL'ICK HELLMUT BENDLER GUNTHER MARONDEL WERNER SIEGELIN av KW D/ I/MffMPM K ATTORNEYS.

METHOD FOR THE RAPID REACHING AND MAINTENANCE OF A CERTAIN TEMPERATURE LEVEL This invention relates to heating devices. It more particularly refers to such devices which use pyrotechnic compositions forheating purposes.

Systems are known which make it possible to raise the temperature of a body rapidly to a certain level and to keep it at that level for a relatively long time. For example, electrical heating coils are used whose output is diminished upon the reaching of a certain predetermined temperature, thereby enabling this temperature to be kept constant over a relatively long period. This method has the disadvantage that it requires expensive and complex apparatus.

The use of pyrotechnic compositions is known only for the rapid heating of bodies. Their action is similar to that of a stove burner or immersion heater; their advantage of very rapid heating, however, is offset by the disadvantage that it has not been possible hitherto to use pyrotechnic charges for the purpose of maintaining a body at a certain predetermined temperature for a certain period of time after the body has had its temperature raised to that predetermined level.

These disadvantages are overcome by the method of the invention, according to which pyrotechnic compositions are used to melt metals or alloys and to keep them at the fusion temperature or in the fusion range over a relatively long period of time. The heat of fusion of the metal or alloy is used as a thermal capacitor. This heat of fusion is yielded over a relatively long period of time to the, body that is to be heated or the system that is to be heated; in this manner the temperature of the body or system is maintained within a range of fluctuation of about percent of the desired level over the given span of time. According to the invention, there is used in combination l a rapidly burning pyrotechnic charge which heats the body and brings the metal or alloy to fusion, and (2) a slowbuming thermal composition which supplies heat to the metal or alloy beyond the reaction time of the rapidly burning pyrotechnic charge and holds it at the fusion temperature or within the fusion range. The excess heat that is yielded is compensated by the heat of fusion of the metal or of the alloy.

A preferred embodiment of the invention will now be explained with the aid of the annexed drawing.

FIG. 1 represents a side elevation and FIG. 2 a plan view of the system according to this invention.

In the drawing, the numbers have the following meaning: I is a metal body containing a system that is to be rapidly heated. In the cylindrical chamber 2 surrounding this metal body is a pyrotechnic charge having a very rapid reaction time. This cylindrical chamber 2 is separated by a thin metal wall 3 from the cylindrical chamber 4 in which there is contained a slowly reacting, energy-rich thermal charge. The thin metal wall 3 is covered on one or both sides by a metal or a metal alloy 5 having a predetermined specific melting point and a specific heat of fusion. lgniters 6 can be located in chamber 2 or in chamber 4; if only one igniter is used, it must be in direct contact with the heating charges in chambers 2 and 4. One or more passages 6a, which are filled with a known combustible composition, make possible such direct contact. Also, two or more igniters connected in parallel or in series can be used.

The pyrotechnic charge in chamber 2 consists of a powdered metal, an oxidant and, if desired, a reaction accelerator. Such pyrotechnical compositions are in the prior art, and their makeup can vary widely; the important thing is that they burn rapidly and rapidly reach a high, given, predetermined temperature. The following are examples of the metals that can be used; silicon, aluminum, magnesium, titanium, zirconium, manganese, beryllium. cadmium, iron, or alloys of same, such as TiAl, FeZrSi, MgAlZnMn. Nitrates, chlorates, perchlorates, chromates and dichromates of alkali, alkalineearth metals or ammonium and oxides which easily yield oxygen e.g. Pb0 Pb 0 Mn0 and organic and inorganic peroxides. are used as oxidants. The reaction accelerators are known reaction accelerators such as boron. (e.g.

The thermal charge in chamber 4 can have the same components as the fast-buming charge in chamber 2, as long as it burns more slowly. Therefore, it is practical that the thermal charge in chamber 4 is the same as or similar to that in chamber 2 but contains no reaction accelerators. The thermal charge percentage composition can vary within the following limits:

Oxidizers 20 to 50 percent by weight:

Metal or alloy powder 80 to 50 percent by weight. The

precise chemical composition of the thermal charge depends on the desired reaction time and the required time of rise of the temperature to a maximum value. Compositions which meet these requirements are known to those skilled in this art andcan easily be prepared on the basis of information contained in the literature for the desired purpose.

The metal wall 3 consists preferably of the same material as the jacketing about the entire system, e.g., steel. This wall 3 serves only to divide the chambers 2 and 4 from one another. The annular metal or metal alloy jacket 5 adjacent to this metal wall consists of any metal or metal alloy; all it needs do is fulfill the requirement that it melt at a temperature that is to be specified, and that it have a selectable predetermined thermal capacity. The following metals are preferentially suited for this purpose; lead, aluminum, copper, silver, gold, an-

. timony, nickel, cadmium, and the various alloys formed by these metals with tin, bismuth, copper, silver, zinc, mercury, iron, platinum, sodium and thallium. The thickness of the jacket is governed by what its then'nal capacity is to be.

The method of the invention permits raising the temperature of bodies or systems to any desired level between 200 C. and l500 C. within 0.1 to 6 seconds, and maintaining this temperature over a period of l to 5 minutes.

The arrangement of the invention can be used, for example, for the purpose of putting a battery into operating condition, i.e., producing a certain battery terminal voltage, by heating an electrolyte to a certain temperature.

EXAMPLE metal cylinder in the center and the lead jacket there is placed.

3.5 g. of a pyrotechnic charge having the following composition:

26 wt; percent K;Cr=01 39 wt. percent silicon powder 35'wt. percent'PbO Also in this cavity there is an electric primer. In the space between the metal jacket and the outer wall there is 14.0 g. of

a thermal charge consisting of:

40 wt. percent KCnO1 and 60 wt. percent silicon powder.

After the ignition of the two thermal charges, the metal cylinder in the center of the arrangement reached a temperature of 650 C. within 3 seconds and maintained that temperature for 3 minutes with a fluctuation of plus or minus 30 C.

We claim:

1. A heating device comprising core means housing a material to be heated; first chamber means about said core means; a first pyrotechnic composition in said first chamber; a meltable metallic wall means about said first chamber; second chamber means about said meltable wall means; a second pyrotechnic composition in said second chamber; igniter means operatively associated with said pyrotechnic compositions; wherein said first pyrotechnic composition has, upon ignition, a faster burning rate than said second pyrotechnic composition sufficient to melt said meltable wall means in a predetermined time and to heat said material to a predetermined temperature in a predetermined time; and wherein said second, slower burning, pyrotechnic composition generates, upon ignition, sufficient heat to maintain said wall means in a molten condition for a predetermined time.

2. A heating device as claimed in claim 1, wherein said meltable wall has a metal support embedded therein which is not meltable by the ignition of said pyrotechnic composition.

3. A heating device as claimed in claim 1, wherein said core, said wall and said body are substantially cylindrical, and wherein said chambers are substantially annular.

4. A heating device as claimed in claim 1, wherein said meltable wall means is an alloy.

5. A heating device as claimed in claim 1, wherein said meltable wall means is a single metal.

6. A heating device as claimed in claim 1, wherein said meltable wall means is at least one member selected from the group consisting of lead, aluminum, copper, silver, gold, antimony, nickel, cadmium and alloys thereof with at least one different metal selected from the group consisting of tin, bismuth, copper, silver, zinc, mercury, iron, platinum, sodium and thallium.

7. A heating device as claimed in claim 1, wherein said pyrotechnic compositions are each composed of a metallic powder and an oxidizer, and wherein said first pyrotechnic composition additionally contains an accelerator.

8. A heating device as claimed in claim 7, wherein said composition comprises about 20 to 50 percent by weight of at least one number selected from the group consisting of nitrates, perchlorates, chlorates, chromates and dichromates of at least one metal selected from the group consisting of alkaline metals and alkaline earth metals or ammonium; about 50 to percent by weight of at least one member selected from the group consisting of silicon, aluminum, magnesium, titanium. zirconium, manganese, beryllium, cadmium-iron. titaniumaluminum alloy, iron-zirconium-silicon alloy, and magnesium aluminum zinc-manganese alloy; and for the first pyrotechnic composition about 0 to 60 percent by weight of at least one member of the group consisting of boron and lead oxide.

9. A heating device as claimed in claim 2, wherein said first pyrotechnic composition comprises about 20 to 50 weight percent potassium perchromate, about 20 to 50 weight percent silicon powder and the remainder lead oxide, wherein said second pyrotechnic composition consists of potassium perchromate and a silicon powder, and wherein said metal support is steel.

10. A heating device as claimed in claim 1, wherein said first pyrotechnic composition is 26 weight percent potassium perchromate, 39 percent silicon powder and 35 weight percent lead oxide; and wherein said second pyrotechnic composition consists of 40 weight percentpotassium perchromate and 60 weight percent silicon powder. 

1. A heating device comprising core means housing a material to be heated; first chamber means about said core means; a first pyrotechnic composition in said first chamber; a meltable metallic wall means about said first chamber; second chamber means about said meltable wall means; a second pyrotechnic composition in said second chamber; igniter means operatively associated with said pyrotechnic compositions; wherein said first pyrotechnic composition has, upon ignition, a faster burning rate than said second pyrotechnic composition sufficient to melt said meltable wall means in a predetermined time and to heat said material to a predetermined temperature in a predetermined time; and wherein said second, slower burning, pyrotechnic composition generates, upon ignition, sufficient heat to maintain said wall means in a molten condition for a predetermined time.
 2. A heating device as claimed in claim 1, wherein said meltable wall has a metal support embedded therein which is not meltable by the ignition of said pyrotechnic composition.
 3. A heating device as claimed in claim 1, wherein said core, said wall and said body are substantially cylindrical, and wherein said chambers are substantially annular.
 4. A heating device as claimed in claim 1, wherein said meltable wall means is an alloy.
 5. A heating device as claimed in claim 1, wherein said meltable wall means is a single metal.
 6. A heating device as claimed in claim 1, wherein said meltable wall means is at least one member selected from the group consisting of lead, aluminum, copper, silver, gold, antimony, nickel, cadmium and alloys thereof with at least one different metal selected from the group consisting of tin, bismuth, copper, silver, zinc, mercury, iron, platinum, sodium and thallium.
 7. A heating device as claimed in claim 1, wherein said pyrotechnic compositions are each composed of a metallic powder and an oxidizer, and wherein said first pyrotechnic composition additionally contains an accelerator.
 8. A heating device as claimed in claim 7, wherein said composition comprises about 20 to 50 percent by weight of at least one number selected from the group consisting of nitrates, perchlorates, chlorates, chromates and dichromates of at least one metal selected from the group consisting of alkaline metals and alkaline earth metals or ammonium; about 50 to 80 percent by weight of at least one member selected from the group consisting of silicon, aluminum, magnesium, titanium, zirconium, manganese, beryllium, cadmium, iron, titanium-aluminum alloy, iron-zirconium-silicon alloy, and magnesium-aluminum zinc-manganese alloy; and for the first pyrotechnic composition about 0 to 60 percent by weight of at least one member of the group consisting of boron and lead oxide.
 9. A heating device as claimed in claim 2, wherein said first pyrotechnic composition comprises about 20 to 50 weight percent potassium perchromate, about 20 to 50 weight percent silicon powder and the remainder lead oxide, wherein said second pyrotechnic composition consists of potassium perchromate and a silicon powder, and wherein saiD metal support is steel.
 10. A heating device as claimed in claim 1, wherein said first pyrotechnic composition is 26 weight percent potassium perchromate, 39 percent silicon powder and 35 weight percent lead oxide; and wherein said second pyrotechnic composition consists of 40 weight percent potassium perchromate and 60 weight percent silicon powder. 